Electron-tube relay



July 22, 1930. M. vos w 1,771,021'

ELECTRON TUBE RELAY Filed Aug. '7, 1929 y Vf *WIT

Patented July 22, 1930 Y y MAURITZ vos, or STOCKHOLM, SWEDEN, Assreivoa rTo'ranni"oivnmrniaonncnT'n111:.

ERICSSON, OFSTOGKHOLIVI, SWEDEN, A COMPANY OF SWEDEN ELnoTRoN-TUBE RELAY V` Application` `led August 7, 1929, Serial No. 384,165, and in Sweden-October 1, 1928.

The present invention relates to Velectron tube relays in which-the grids belonging to two mutually parallel-connected anodes are i subjected vto alternating potentials having y equal amplitudesfbut opposite phases. In this known arrangements the static characteristic of the combined relay may be repre sented by a diagram which is nearly parabolic and symmetrical in relationito oneof the coordinate axes; VOn the Vother hand, the dynamic characteristic indicating the opera- `tionot the relays will in the known arrangement deviate `from the static one,`on account of the reaction'exerted upon the resulting control voltage in thetubes andVV Acaused by the drop of voltage inthe outer' impedance 1 of the anode circuit. The invention haspfor its object to establish a relation between the anode current and thegrid voltagefwhich relation is as simple as possiblek and is furthering the modulation or the demodulation respectively. According to the inven- Ation a compensating voltage'is back-coupled from the anodecircuit common to the anode's, to the two grids with the same phase and amplitude and in such amanner that the reaction of the anodeload lupon the control voltages Vis substantially compensated.r Also n for thedynamic characteristic one` may then `obtain a parabolapractically completely `conforming with the static characteristic whichv curve represents the ideal shape; of achaiacteristicV in amodulatorf orv demodulator. This results in the disappearanceof most Vof `the higher harmonics otherwise occurring in the anode current on account ofv said "reaction, Furthermore* thel advantage'is "ilo gained that the relay device may be subjected to an easy and Vexact pre-calculation in contradistinction to the conditions" inhither'to known electron tube relays used for thesame purpose. d The invention will beI more"close1yffde scribedwith reference to the accompanying drawing in which; Figures land 2show two known arrangements in electrontube'relays ofthe present kind in vordertorender clear :relay is composed of two ordinary. threef` 'electrode tubes' 1, 1, the anodes 2,2 of which d Figure 2 ldiiiers from to `the invention in whichthereaction of the i. anode load is compensated whereas Figure 4 shows a diagram of a characteristic. y l, Y

In allrtheshown circuit arrangements the are connected in parallel .in relation to each other and also connected to the one terminal of a coil'*3"the other terminal of which is connected to the positive pole of the anode battery 4. The coil 3 is inductively coupled to a secondary coil 5 "from which the modulated or cle-modulated oscillations maybe tapped olf.` A

In the circuit arrangement according to Figure 1 the grids 6, 6 of the two tubes are connected each to one end of the secondary coil 7 of a transformer the `primary terminals 8 of which constitute the inputv terminals of the relay. The secondary winding? is- 10 provided V'with an intermediate tapping, 9 to which a grid biasing battery 10 may be connected.` Hf 'e 4The circuit arrangement l according toV therein that the grids 6, 6 are directly connected each to one oflthveinput terminals 8 Vbetween which an impedance 11 provided Vwith ajmiddle pointtapping 12 is interconnected. may be connected.

y As the alternating potentials ott-he Vgrids 6, 6" lhave mutually exactly opposite phases the static characteristic of the two. tubes may, y.

relation to one of the coordinate axes. In

the diagram Vr represents the amplitude of the Lcontrol .1 alternating voltages according l. to the formula i 9 relating to the twotubes, 1, 1. The relations between the anode currents of theV tubes represented za, cfa', and the controlalterynating voltage Vr and vjrespectivelymay be analy mulas the preceding one only To said point the biasingbattery10S `in the diagram in Figure 4 be represented 85 vby two curves-extending symmetrically in really expressed thrcugh thefcr- If the tubes are exactly equal the corresponding constants are alike.

If it is assumed that the primary circuit of the input transformer includes a high frequency generator of the frequency w1 and a modulating current source of the frequency e2, by way of example, falling within the range of voice frequentoscillations, we have Vg=A1 SlIl wld-Z Sll'l w25 According to Formula 1 VFA. sin wenn sin a2f+%+ V.,

in which formulas the last terms correspond to the compensating voltage transferred back to the grid circuit from .the anode circuit. According to the present invention said voltage is so adjusted that The resulting control voltages are then V,-=A1 sin wit-l-h-Ag sin ezt and l7,= x41 sin Dlt-A2 sin egt: -V,-. The resulting anode current Ia in the coil 3 is then obtained by insertion into the Equation 2, thus Said resulting anode current is in the diagram in Fig. 4 represented by the parabolic curve drawn in full lines. In most cases it is possible in the last equation to neglect terms of higher powers than the second for which reason the curve Ia may be considered as practically an exact parabola.

The term essential to the modulation in the expression for Ia is then according to Formula 4 'be fulfilled by a suitable selection of the grid direct current'biasing voltage according to Figure 4 so as to obtain said point at the verteX of the parabola, (A in Figure 4), or in other words in such a way that the resulting control direct current voltage The suppression of the carrier wave brings certain advantages in case the modulating oscillations, according to the invention, are transferred from a modulator to a power amplifier before they are supplied to an antenna or the like. By the suppression of the carrier wave the power amplifier is, namely, unloaded therefrom and operates thus more economically.

In case the reaction of the anode load upon the control alternating voltages Vr and V. had not been eliminated by rendering the control alternating voltages would have been functions of the anode current as Va=ZaLl in which expression Za designates the outer anode impedance. When adding the Equation 2 the result would thus be an implicit expression with respect to the anode current. The pre-calculation of the apparatus is thus rendered dillicult and the explicit solution with respect to la will contain also terms which are not negligible. By compensating the reaction of the outer anode impedance in above described manner according to the present invention said inconvenience may, however, be eliminated and a dynamic characteristic coinciding with the static characteristic of thedesired pure parabola shape is obtained. To bring about said compensation one may according to the invention as shown in Figure 3 include a. retransfer coil 13 in series with the grid biasing battery 10 which coil is inductively coupled to the primary coil 3. The degree of coupling between the coils 3 and 13 is so adjusted that the reaction of the anode load is substantially compensated which occurs if the retransferred voltage V., is made equal In this case the control voltage wise would occur on account of the reaction of the anode circuit. The arrangement may also be subjected to a completely exact precalculation.

In addition to the above manner of compensating the reaction of the Vanode circuit upon the grid circuit there are also other possibilities conceivable to obtain nearly" the same result of the compensation. One may, by way of example, use so called shielding grid tubes in which, by the disposition of a fourth electrode of a constant potential in the tube, the reaction of the anode circuits upon the grid circuit to 'a certain degree is compensated."

In certain cases it is, however, not desirable to suppress the carrier wave. The point of operation should in such a case not fall at A but be displaced, by way of-example, to the point A in Figure 4. Also in this case, however, a modulated oscillation in the anode circuit is obtained, because the dynamic characteristic is practically an exact parabola, which oscillation is free from harmonics and is proportional to the product of the amplitudes of the modulating and the modulated grid alternating voltages. Such an absence of higher harmonics is, on the other hand, not obtained in hitherto known embodiments of electron tube relays for modulation or demodulation.

I claim:

A11 electron tube relay comprising two .Y

MAURITZ VOS. 

